The present invention relates to an elongated electroluminescent light strip and to a continuous process for making such a strip. More particularly, the present invention relates to elongated electroluminescent light strips useful as moldings for vehicles and as building pathway and other light marking strips and to a continuous method of making such strips.
Electroluminescent lights have been known for many years and have been made by using conventional sheet lamination techniques to make a laminate structure of layers of a phosphor matrix sandwiched between electrically conductive layers. Typically, the electrically conductive layers include an aluminum foil layer and a conductive transparent sheet such as a layer of indium tin oxide. The foil can be insulated from the phosphor matrix by a dielectric coating. The electroluminescent lighting or lamp is often covered with a transparent moisture barrier film such as a polychlorotrifluoroethylene film.
Recently there has been development of electroluminescent technology for backlighting instruments and computer screens and for ornaments for vehicles. Three recent U.S. patents employing electroluminescent lamps in association with vehicles are U.S. Pat. Nos. 4,443,832 Apr. 17, 1984 to Kanamori et al. for "Self-illuminating Ornament for Vehicles; 4,494,326 Jan. 22, 1985 to Kanamori for "Electroluminescent Display Structure for Motor Vehicle Window" and 4,603,065 Jul. 29, 1986 to Mori et al. for "Decorative Part." An elongated electroluminescent light strip has also been developed and is disclosed in U.S. Pat. No. 3,161,797 Dec. 15, 1964 to Butter et al. for "Electroluminescent Device."
Conventional electroluminescent light techniques have encountered several problems. The phosphor matrix is extremely sensitive to moisture and one problem encountered in electroluminescent lamp construction relates to the destructive effect water vapor has on the phosphor layer. In a conventional laminate construction, a desiccant layer is sometimes used along with protective films having low vapor transmission rates to increase the longevity of the life of the phosphor matrix. The prevention of moisture encroachment into the lamp's interior is of paramount importance in electroluminescent light construction. This is especially true with the electroluminescent lamps sealed in an Aclar envelope. Typically, the Aclar electroluminescent lamps have wire leads which provide a place for moisture to enter the lamp.
Conventional lights are generally made of relatively thin construction with the protection film having edges either adhesively bonded or thermally fused using high pressure rollers. The thin protection film provides marginal protection against moisture ingress and high pressure rollers, i.e., conventional sheet lamination techniques, can damage the thin, fragile layers of the electroluminescent light. Conventional lamination techniques also, of course, can lead to wrinkles which are unsightly and can lead to moisture ingress into the light's interior. Thermally fusing leads to another problem, i.e., possibly damaging the phosphor matrix by excessively heating it. Another problem generally encountered in lamp construction relates to the relatively fragile nature of the various layers and of the lamp itself. Traditionally electroluminescent lights have been constructed to be as thin as possible and hence have had little inherent structural integrity. The electrically conductive layers are subject to damage during processing and, if wires are incorporated into the light, they tend to damage the other layers during manufacture of the light.
Thus, there remains a need for an improved electroluminescent light strip and for an improved continuous process for making an elongated electroluminescent light strip. In particular, there remains a need for an improved process in which the moisture sensitive electroluminescent lamp is well protected from the environment and which provides an electroluminescent lamp having good structural integrity. Also, as will be apparent to those skilled in the art, it would be desirable to have an economical, continuous process for making an elongated electroluminescent light strip.